gruntjs/grunt-contrib-imagemin — pull request #19 by crowjonah (2013-02-27 22:51:39+00:00)
Title: Limit image optimizations to 10 at a time

I saw Issue #15 after having had the same issue myself.

(node) warning: possible EventEmitter memory leak detected. 11 listeners added. Use emitter.setMaxListeners() to increase limit.

This seems to fix the problem for me, though it doesn't mean that there might be a better fix out there involving `removeAllListeners` or something.